The invention relates to attachable couplings for hose, but more particularly, the invention relates to a deformable ferrule for use in coupling hose.
Couplings that are post-assembled to flexible hose typically have a male stem portion that is insertable into a hose end and a ferrule that is concentric with the male stem. The ferrule may be pre-attached to the male stem or post-attached to the male stem during a coupling process requiring deformation of the ferrule. Together, the male stem and ferrule define an annular cavity for receiving a hose end. The coupling is retained to the hose end by pinching or compressing it between the ferrule and stem. The ferrule may be pre-attached to the stem such as by crimping an end portion of the ferrule to a stem collar so that the annular hose receiving cavity is formed. A ferrule as a separate part, may be attached to a collar of the stem when the ferrule is deformed such as by crimping or swaging.
Some ferrules have a smooth bore and are deformed during crimping to provide what is known as a "ripple crimp" where a plurality of annular ridges and grooves are formed in the ferrule sidewall. The male stem may have a plurality of annular serrations or grooves to aid in gripping a hose end when a ferrule is deformed during the coupling process.
In some applications, circumferential, helical, or longitudinal ribs are provided on the inside of the ferrule to aid in gripping a hose end. Such ribs may contact an embedded reinforcement of the hose for greater coupling retention. The ferrules may be deformed to a generally cylindrical exterior shape such as by crimping or swaging.
A pre-attached ferrule having a constant wall thickness and a frusto-conical shape to aid in inserting a hose end prior to deformation is shown in US-A-3530900. During the coupling process, the frusto-conical shaped ferrule is crimped to have a generally cylindrical shape with a plurality of circumferential ribs and grooves that co-operate to pinch the hose end.
A post attached ferrule is exemplified by US-A-4305608. The ferrule has a plurality of longitudinally oriented ribs that are capable of penetrating a hose cover to embed with a hose reinforcement when the ferrule is deformed to have a generally cylindrical exterior shape. During crimping, portions of the ribs are deformed against a stem collar to define a means for attaching the ferrule to the male stem.
Another example of a pre-attached ferrule is shown in US-A-4226446. A serrated stem and ferrule with a "ripple crimp" is used to pinch a hose end and retain a coupling. A difference in the pitch spacing between a "ripple crimp" and serrations on a male stem causes the hose to be pinched in progressively reduced amounts of compression even though the ferrule and stem define a generally annular cavity for receiving the hose end. While reduced pressure zones are recognised as being beneficial to minimise local stresses in a coupled hose end for improving coupling retention, special care must be taken to ensure that the pitch spacing of the ripple crimp is properly located with respect to the pitch spacing of the male stem so that reduced pressure zones are achieved.
Although US-A-3530900 shows generally a pre-crimped frusto-conical cavity for receiving a hose end, it and US-A-4226446 and 4305608 show post-crimped annular cavities for pinching or compressing a hose end. Of these, only US-A-4305608 appears suitable for high pressure hose applications as indicated by ferrule ribs directly contacting a hose reinforcement.
Also, US-A-2028316 shows a ferrule with circumferential ribs and a tapered outside diameter, in which the ribs are forced inwards when the ferrule is deformed.
As has been said, it has been recognised that reduced pressure zones near the hose end can be beneficial, though certain problems must be taken into account. GB-A-1294132 shows a deformable ferrule for use in coupling a hose comprising a sleeve type body with an outer surface, an inner surface, a fitting end and a hose end, wherein the body has a sidewall portion that decreases in thickness longitudinally of the body toward the hose end, so that, after deformation of the body when coupling a hose the outer surface has a generally cylindrical shape, and the inner surface juxtaposed said sidewall portion has a generally frusto-conical shape. By this means, upon swaging, pressure on the hose is greater at the fitting end than at the hose end. That ferrule has annular grooves or screw threads on the inner surface. These grooves cause the wires of the hose braiding to undulate, causing stress concentration where the wires are forced to bend tightly. This phenomenon is particularly marked at the fitting end where it can cause failure of the wires. In the device described in the GB patent, this is particularly marked because the grooves are deeper at the fitting end.
It would be desirable to provide a hose ferrule that controls decreasing pinching or compressing of a hose end during crimping, in a direction from a fitting end of the ferrule toward the hose end of the ferrule, and at the same time avoid conditions which might lead to failure of the braiding wires and provide as high resistance to axial pull-out as possible.
According to the present invention, a deformable ferrule is provided as in the precharacterising part of claim 1 wherein a plurality of generally parallel and circumferentially spaced apart ribs extend from the inner surface and are generally longitudinally orientated with the body, so that after said deformation of the body to give the outer surface a generally cylindrical shape, the ribs are generally orientated as frusto-conical elements of a cone wherein the circumferential spacing between ribs near the fitting end is smaller than the circumferential spacing between the ribs near the hose end.
It is found that by providing such ribs in a ferrule of this description, a greater pull-out force is achieved than would otherwise be expected from the characteristics of existing ferrules which have longitudinal ribs which are not generally orientated as frusto-conical elements of a cone.
According to the present invention, there is also provided a method for providing a frusto-conical surface portion along an inside surface of a ferrule to effect progressively reduced amounts of compression when coupling a hose, comprising the steps of providing a ferrule having a sleeve-type body with a fitting end, a hose end an inner surface and an outer surface which, with the inner surface, defines a sidewall portion of the ferrule that decreases in thickness longitudinally of the body toward the hose end, and deforming the ferrule to have a generally cylindrical outer surface while simultaneously forming a frusto-conical surface portion along the inner surface of the ferrule, characterised in that a plurality of generally parallel and circumferentially spaced apart ribs extend inwardly from the inner surface, substantially longitudinally orientated with the body so that after deforming the ferrule, the ribs are generally orientated as frusto-conical elements of a cone wherein the circumferential spacing between ribs near the fitting end is reduced and is smaller than the circumferential spacing between ribs near the hose end.
Several embodiments of the invention are now described by way of example with reference to the accompanying drawings, wherein:-
Referring to Figures 1 to 6, the ferrule 10 of the invention includes a sleeve-type body 12 having a fitting end 14, a hose end 16, a substantially cylindrical inner surface 18, and an exterior surface having a frusto-conical surface portion 20 and, optionally, a cylindrical surface portion 22. The inner surface 18 and outer surface portion 20 outline a sidewall portion 24 that decreases in thickness going longitudinally of the body 12 toward the hose end 16. A plurality of circumferentially spaced ribs 26 are oriented longitudinally of the body and project from the inner surface. The ribs may extend a major length of the body and ends of the ribs may be tapered 28.
. In service, the ferrule is used with a male stem 30 having some type of fitting 31 at one end and optionally a serrated stem 32 at the other end. The ferrule is slipped over an end portion of a hose 34 constructed with a tube 36, reinforcement 38, and cover 40 as exemplified by Figure 4. The stem may also include a locking collar 42 for securing the ferrule to the stem in a manner as described in US-A-4305608. The male stem is inserted in the hose bore and the ferrule is deformed by reducing it in diameter, such as by crimping or swaging, as illustrated by Figures 5 and 6. During deformation, the outer surface is changed to a generally cylindrical shape 44 and the inner surface is changed to a generally frusto-conical shape 46. The ribs change from being what may be described as longitudinal elements of a cylinder (Figure 3) to frusto-conical elements of a cone (Figure 6). Grooves 48 are formed in the ribs by the collar 42 and the hose reinforcement 38 is partially embedded 50 into portions of the ribs upon ferrule deformation. The ribs grip the reinforcement and the inner surface grips the hose end in a constantly decreasing manner progressively to reduce the amount of hose compression or pinching and thereby eliminate localised high stress points in the coupled hose at the hose end of the ferrule. The amount of reduction in wall thickness to effect a usable coupling will, of course, vary for different hoses and different applications. It has been determined that a satisfactory coupling is achieved when the outer frusto-conical surface portion has a half conical angle A up to about 4°. The cylindrical surface portion acts as an aid to reduce coupling skewing during crimping by being the first surface contacted and held by radially moving cylindrical elements of a crimping machine of the type well known in the art.
Additional examples of ferrules of the invention are illustrated in Figures 7 and 8. Both of the ferrules exhibit a sidewall portion 24 that decreases in thickness going longitudinally of the ferrule toward the hose end 16. Both of the ferrules exhibit on deformation, an outer surface that is generally cylindrically shaped and an inner surface portion that is generally frusto-conically shaped. More specifically, Figure 7 illustrates a ferrule 52 having a frusto-conical outer surface 54 at a half angle B and a frusto-conical inner surface 56 at a conical half angle C. The angles B, C need not be equal. Longitudinally oriented ribs 58 extend from the interior surface as elements of the frusto-conical surface 56. In use, the outer surface 54 is deformed to a generally cylindrical section in a manner described in reference to Figures 5 and 6. Such deformation increases angle C.
Figure 8 illustrates a ferrule 60 having a generally cylindrical outer surface 62 and a frusto-conical inner surface 64 having a conical half angle D. During deformation the ferrule is reduced to a smaller diameter with the outer surface remaining substantially cylindrical and the inner surface remaining frusto-conical so that the hose end receives progressively reduced amounts of pinching or compression. Longitudinally oriented ribs 66 extend along the inner surface as elements of the frusto-conical surface 64.
If desired, a collar (not shown) may extend from the body at the fitting end 14.